A jeweller and his wife who disposed of crucial evidence after their jealous son murdered his teenage girlfriend have been jailed for 27 months each.

Elliot Turner, 20, was found guilty by a jury of strangling 17-year-old Emily Longley in a rage because he suspected she was seeing other men.

His parents, Leigh, 54, and Anita, 51, were jailed for perverting the course of justice by destroying a letter of confession written by their son and concealing a jacket they thought might have linked him to the killing, which took place at their home in Bournemouth, Dorset.

Sentencing the couple, Mrs Justice Dobbs said: "I appreciate it must be very difficult for a parent when faced with the situation you found yourself in but you well knew what you did was wrong and against the law."

She said the act of destroying a confession letter was a "very serious offence" and added: "It strikes at the integrity of the criminal justice system."

The judge said she understood that Mrs Turner was still coming to terms with the fact her son was a convicted murderer. She told Mr Turner that although he had expressed remorse for Emily's death, he had not demonstrated regret for his own actions.

She added: "I take into account you are people of previous good character. People speak highly of you both and it's a tragedy that you, who are both respectable people, have lost that by acting out of misplaced loyalty. It must be hard for you to come to terms with what the jury found your son did."

The court heard that Mr Turner destroyed the confession letter written by his son with the agreement of his wife. Mrs Turner removed the jacket from the crime scene as she feared it would implicate Elliot.

Their actions were uncovered when police bugged their house and recorded conversations in which they discussed whether they had done the right thing.

Fern Russell, representing Mrs Turner, said: "She is a mother who couldn't accept that her son had committed the worst imaginable crime and it was in that turmoil that she carried out that act. In her mind she wasn't concealing a murder but at worst was buying time for her son to explain himself."

Robert Grey, defending Mr Turner, said he had acted when his mind was in turmoil at discovering what his son had done. He said: "He has to live with the fact his son is a convicted murderer. That knowledge can itself amount to a form of punishment and the court knows his life has been affected by what has happened in the past 15 months or so. The defendant is deeply depressed."

Speaking outside Winchester crown court, Emily's grandfather, Ron Longley, said: "Today brings a sort of conclusion to a dreadful year. Mr and Mrs Turner are very fortunate in how much compassion the judge showed in the mitigating factors. We are satisfied with the sentence, we feel it was balanced and just.

"A year ago, Mr and Mrs Turner's son murdered my granddaughter Emily, our lovely, shining Emily. This presented Mr and Mrs Turner with a dreadful dilemma. They made the wrong decision.

"As a result, we and many other people have spent a long year and more waiting for this. Because of their actions, the police were forced into a prolonged, protracted and expensive inquiry. Thank goodness they were so very thorough and professional – we will be forever grateful for them for that."